What CPU load you see (in Windows Task Manager - Performance tab) on all cores when this is set to 50%?
Do you see only 3 CPU tasks running (in BOINC Manager - Tasks, in Windows Task Manager - Processes)?

Try even lower setting as 1% (I'm not sure will this use 0 or 1 core (i.e. no CPU tasks running at all or just one CPU task))

Change for test to <count>1</count> (make copy of original app_info.xml for easy return)

Also check what is 'angle range', only compare times for "similar" AR tasks:
"WU true angle range is" in stderr.txt (in ....\BOINC\slots\ while the GPU tasks run)
<true_angle_range> in the task/WU file

With 3 cores active, I was getting the load that varied between 50 and 55%. Setting it to run just 1 core (1% setting) gave the load between 16 and 21%. Changing the count to 1 too didn't seem to bring about any change.

1. I was getting high reading (max of 22k microsec) at frequent intervals. Following their suggestion, I disabled the network card and the frequency and the maximum values dropped.

2. I also noticed the EVGA Precision X was using a high % of CPU so shut that down as well which further reduced the latency.

3. Next to be disabled were the nVidia HD Audio. After this I started getting low reading with max of 1850 microsec.

I left the system running for sometime, during which a blank screen saver that I had set, kicked in. Upon returning, I logged back in and although the latency was still under 1000 microsec, one of the GPU had started a slow motion stunt.

So the next step was to disable the screen saver.

I did a drivesweep and fresh installation of the LAN driver. And just to be sure, I did a clean installation of the graphics driver with both the cards in the system. I enabled the network card and the latency was within permissible levels with occasional spikes.

Finally I put back the max CPU cores to be used back at 100% and the both the GPUs, as of now have been crunching without any hiccups since last night.

The rig has been under observation for many hours now and still seems to be doing well than before, and hope it stays that way. Not really sure if the nVidia HD Audio has any adverse effects but I shall keep it disabled, and also the screensaver. The network card has to be active for obvious reasons.

I have to thank you all for your advice and expertise. And thanks to BilBg for the Latency Checker. There are still some spikes now and then but the crunching looks smooth.

screensaver you say? That might be a clue. Do you have your power settings set to never turn off monitor and always disable any screensaver including the BOINC/seti ones.
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In a rich man's house there is no place to spit but his face.
Diogenes Of Sinope

When installing the driver choose manual/custom/advanced or whatever it is that it says and then untick all the boxes (3-4 boxes). The actual graphics driver (if I'm remembering this correctly) you can't uncheck even if you wanted to. The rest of the stuff you don't need.

And of course, don't forget to check/tick the "clean install" box/option. Wish I could be more help with the problem you are having but I don't have the experience.

I changed my bios settings for mem timings to all auto--speed and timings. Previously it was running at 1333 7-7-7-21 (which it is rated for under an XMP profile), "auto" wanted it to 1066 7-7-7-20 which is JEDEC #2 (so says cpu-z).

Latency checker then reported values 15-30.

I tried tightening the timings to 6-6-6-auto, which runs, but the latency goes back up to ~100.

Has anyone come across the following message under status in the Tasks list - 'Waiting to run (0.04 CPUs + x.xx NVIDIA GPUs) (waiting for GPU memory)', even though GPU-Z reports memory usage at around 50%?

Has anyone come across the following message under status in the Tasks list - 'Waiting to run (0.04 CPUs + x.xx NVIDIA GPUs) (waiting for GPU memory)', even though GPU-Z reports memory usage at around 50%?

I had this issue before, in my case happens when for some reason the nvidia driver is corrupted, for example if you try to do remote access with RDP. Normaly restarting the computers solve the problem.
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I had this issue before, in my case happens when for some reason the nvidia driver is corrupted, for example if you try to do remote access with RDP. Normaly restarting the computers solve the problem.

I use RealVNC to connect to this rig, however, it never used to give this message. And yes, restarting the rig solves the issue until I access it again. Hopefully a clean reinstallation of the graphics driver will solve this.

I had this issue before, in my case happens when for some reason the nvidia driver is corrupted, for example if you try to do remote access with RDP. Normaly restarting the computers solve the problem.

I use RealVNC to connect to this rig, however, it never used to give this message. And yes, restarting the rig solves the issue until I access it again. Hopefully a clean reinstallation of the graphics driver will solve this.

This may not be a problem with your video driver, it may be a problem with the graphics drivers that RealVNC uses, just as if you were using RD. The reason I say this is because you are displaying the exact symptoms I had when using Windows RD. I found that LogMeIn (also free) did not cause this problem. It was members of this group that pointed me in the right direction at the time.
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